UpdateProducts2.cs

        private void UpdateProducts() {
            using (var context = new MyEntities()) {
                using (var cn = context.Database.Connection) {
                    cn.Open();
                    using (var tr = context.Database.Connection.BeginTransaction()) {
                        try {
                            //1. ADO.NETで独自のSQL文を実行。
                            var sql = "UPDATE [Products] SET [Price] = [Price] * 1.1 ";
                            var cmd = cn.CreateCommand();
                            cmd.Transaction = tr;
                            cmd.CommandText = sql;
                            cmd.ExecuteNonQuery();

                            //2. DbContextでProductsを更新。
                            var product = context.Products
                                                .FirstOrDefault();
                            product.Price /= 1.1M;
                            context.SaveChanges();

                            tr.Commit();

                        }
                        catch (Exception) {
                            tr.Rollback();
                            throw;
                        }
                    }
                }
            }